[llvm] [AMDGPU] Post-RA Peephole for latency-hiding and hazard-avoidance bet… (PR #191319)

[Shilei Tian via llvm-commits]

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shiltian wrote:

```suggestion
  for (MachineInstr *I = MI->getPrevNode(); I; I = I->getPrevNode()) {
    if (!I->isDebugInstr())
      return I;
  }
```

https://github.com/llvm/llvm-project/pull/191319